Conventionally, a derailleur for the bicycle is often provided with a linkage mechanism comprising four members: a base member, a pair of linkage members pivoted thereto through a pair of connecting shafts, and a movable member pivoted to the linkage members through a pair of connecting shafts and having a chain guide, so that a control wire is operated to transform the linkage mechanism, thereby moving the movable member with respect to the base member.
This derailleur is provided with a wire fixture for fixing one end of the control wire, the fixture mainly using a connecting shaft for connecting the movable member to the linkage members, mounted at the lower surface of the movable member, and projecting downwardly therefrom. Incidentally, there are some derailleurs which provide the wire fixture at an intermediate portion of one linkage member, in which the fixture also projects downwardly from the lower surface of linkage member. In addition, the above terms "the lower surface and downwardly" are used with respect to the mounting condition of the derailleur to the bicycle, which is the same in the following description.
The wire fixture comprises a wire hold base and a tightening screw screwable therewith so that the control wire is secured at one end between the base and the head of the screw.
The control wire is supported at one end to an operating lever through a retainer and secured at the other end to the derailleur when mounted to the bicycle frame.
The wire fixture as abovementioned is mounted to the lower surface of the movable member or linkage member and the tightening screw screws with the holding base from below. Hence, in a case where the control wire is to be secured to the wire fixture, or the wire length is adjusted, the screw is operated at the lower surface of the derailleur, so that the fixing or length adjustment of the wire, is not easy to carry out.
Also, the wire fixture, which largely projects downwardly from the derailleur, is liable to hit a foreign object, thereby creating the problem in that the wire fixture, and in turn the derailleur, is subjected to a large impact so as to be breakable and also has a poor external appearance.
Furthermore, a wire fixture has been proposed which is mounted inside the movable member not to project to the exterior. In this case, however, a window through which a jig operates the wire fixture, is required to be formed at the outer linkage member, thereby also creating the problem in that the outer linkage member has a lowered strength and the derailleur has a very poor appearance.